/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.commons.path.fa.dfa;

import org.apache.iotdb.commons.conf.IoTDBConstant;
import org.apache.iotdb.commons.path.PartialPath;
import org.apache.iotdb.commons.path.fa.IFAState;
import org.apache.iotdb.commons.path.fa.IFATransition;
import org.apache.iotdb.commons.path.fa.IPatternFA;
import org.apache.iotdb.commons.path.fa.dfa.graph.DFAGraph;
import org.apache.iotdb.commons.path.fa.dfa.graph.NFAGraph;
import org.apache.iotdb.commons.path.fa.dfa.transition.DFAPreciseTransition;
import org.apache.iotdb.commons.path.fa.dfa.transition.DFAWildcardTransition;
import org.apache.iotdb.commons.utils.TestOnly;

import java.util.*;
import java.util.concurrent.atomic.AtomicInteger;

public class PatternDFA implements IPatternFA {

    private final List<IFATransition> preciseMatchTransitionList = new ArrayList<>();
    private final List<IFATransition> batchMatchTransitionList = new ArrayList<>();
    // Map<AcceptEvent, IFATransition>
    private final Map<String, IFATransition> transitionMap = new HashMap<>();
    private final DFAGraph dfaGraph;

    // cached
    private final Map<String, IFATransition>[] preciseMatchTransitionCached;
    private final List<IFATransition>[] batchMatchTransitionCached;

    public PatternDFA(PartialPath pathPattern, boolean isPrefix) {
        // 1. build transition
        boolean wildcard = false;
        AtomicInteger transitionIndex = new AtomicInteger();
        for (String node : pathPattern.getNodes()) {
            if (IoTDBConstant.ONE_LEVEL_PATH_WILDCARD.equals(node)
                    || IoTDBConstant.MULTI_LEVEL_PATH_WILDCARD.equals(node)) {
                wildcard = true;
            } else {
                transitionMap.computeIfAbsent(
                        node,
                        i -> {
                            IFATransition transition =
                                    new DFAPreciseTransition(transitionIndex.getAndIncrement(), node);
                            preciseMatchTransitionList.add(transition);
                            return transition;
                        });
            }
        }
        if (wildcard || isPrefix) {
            IFATransition transition =
                    new DFAWildcardTransition(
                            transitionIndex.getAndIncrement(), new ArrayList<>(transitionMap.keySet()));
            transitionMap.put(transition.getAcceptEvent(), transition);
            batchMatchTransitionList.add(transition);
        }

        // 2. build NFA
        NFAGraph nfaGraph = new NFAGraph(pathPattern, isPrefix, transitionMap);

        // 3. NFA to DFA
        dfaGraph = new DFAGraph(nfaGraph, transitionMap.values());
        preciseMatchTransitionCached = new HashMap[dfaGraph.getStateSize()];
        batchMatchTransitionCached = new List[dfaGraph.getStateSize()];
    }

    @Override
    public Map<String, IFATransition> getPreciseMatchTransition(IFAState state) {
        if (preciseMatchTransitionCached[state.getIndex()] == null) {
            preciseMatchTransitionCached[state.getIndex()] =
                    dfaGraph.getPreciseMatchTransition(state, preciseMatchTransitionList);
        }
        return preciseMatchTransitionCached[state.getIndex()];
    }

    @Override
    public Iterator<IFATransition> getPreciseMatchTransitionIterator(IFAState state) {
        if (preciseMatchTransitionCached[state.getIndex()] == null) {
            preciseMatchTransitionCached[state.getIndex()] =
                    dfaGraph.getPreciseMatchTransition(state, preciseMatchTransitionList);
        }
        return preciseMatchTransitionCached[state.getIndex()].values().iterator();
    }

    @Override
    public Iterator<IFATransition> getFuzzyMatchTransitionIterator(IFAState state) {
        if (batchMatchTransitionCached[state.getIndex()] == null) {
            batchMatchTransitionCached[state.getIndex()] =
                    dfaGraph.getTransition(state, batchMatchTransitionList);
        }
        return batchMatchTransitionCached[state.getIndex()].iterator();
    }

    @Override
    public int getFuzzyMatchTransitionSize(IFAState state) {
        if (batchMatchTransitionCached[state.getIndex()] == null) {
            batchMatchTransitionCached[state.getIndex()] =
                    dfaGraph.getTransition(state, batchMatchTransitionList);
        }
        return batchMatchTransitionCached[state.getIndex()].size();
    }

    @Override
    public IFAState getNextState(IFAState currentState, IFATransition transition) {
        return dfaGraph.getNextState(currentState, transition);
    }

    @Override
    public IFAState getInitialState() {
        return dfaGraph.getInitialState();
    }

    @Override
    public int getStateSize() {
        return dfaGraph.getStateSize();
    }

    @Override
    public IFAState getState(int index) {
        return dfaGraph.getState(index);
    }

    @Override
    public boolean mayTransitionOverlap() {
        return false;
    }

    @TestOnly
    public List<IFATransition> getTransition(IFAState state) {
        return dfaGraph.getTransition(state, transitionMap.values());
    }
}
